In Cydia install MobileTerminal and install top.
Open MobileTerminal, enter top and hit return.
Double tap the black screen to let the keyboard disappear.
Now u see a list of all the processes running.
bash, top and Terminal are used by MobileTerminal.
If Springboard is constantly using more than 10% CPU, one Winterboard setting is causing the slow down.
My Springboard has around 10% with having 1 Theme, 1 Battery and Veency enabled.

To kill a process:
- double tap screen to get keyboard
- enter Shift+s and hit return
- enter 9 and hit return
- enter the PID number of the process u want to kill and hit return
To exit top, enter q.
To exit MobileTerminal, exit top first, then single tap screen, select exit and hit return.

Warning!
Do NOT kill processes with lower PID than Springboard.
Will cause Freeze eventually and u need to reboot.
Also if u kill bash or Terminal, it will close MobileTerminal.